Sen. David Vitter of Louisiana has asked the Senate’s ethics committee to investigate Sen. Barbara Boxer — who happens to chair the panel — and Majority Leader Harry Reid for reportedly drafting legislation that would tie an Obamacare-related vote to past acts by lawmakers, a measure that would dredge up Mr. Vitter’s prostitution scandal from years ago as payback for meddling with the health care law.

Mr. Vitter, a Republican, does not make reference to his prior acts in his letter requesting the investigation, but he refers to a Politico story published Friday that says Democrats prepped legislation saying lawmakers would be denied employer contributions to their health care if there was probable cause to believe they solicited prostitutes.

Mr. Vitter was implicated in the “D.C. Madam” prostitution scandal in 2007. He apologized for coming a “very serious sin,” but did not face ethics charges because the alleged incidents occurred before he was a senator.

Now, news reports suggest he might face blowback for trying to reverse a decision by the Office of Personal Management that says lawmakers and their staffs will receive their standard employer subsidy to offset health care costs, even though they must enter state exchanges set up by the Affordable Care Act.

Mr. Vitter and other Republicans say Democrats are trying to exempt themselves from a provision in the law they muscled through Congress in 2010. He said the reported draft bill designed to get back at him is highly inappropriate.

“This is attempted bribery, and the exact sort of behavior that the Senate Ethics Committee has previously condemned,” he said.

In his letter, Mr. Vitter asked the Senate Select Committee on Ethics to recuse Ms. Boxer from any investigation, because she serves as chairwoman.

“It is absurd on its face to think that the Committee can fairly and impartially address the potential ethics violations outlined herein when the Committee’s Chair and her staff appear to have orchestrated them in the first place, or at best were aware of them and did nothing to stop the violations, therefore becoming co-conspirators,” he wrote.